Oh dear! We're falling over them, even I have a B81 under a tarp and do remember a huge number of engine parts are common across the range from B40 upwards.

Obviously blocks, cranks, cams, manifolds, heads, pistons (3.5" or 3.75") and carbs have to differ across the range, but most everything else inside is common; there are only two distributors even, one for the sixes and one that does the fours and eights - as they treat the eights a two fours joined.

R.